Reenforced-concrete pipe



w. 's. HEWETT.

REENFORCED CONCRETE PIPE.

APPLICATION FILED JUNE 27, 1921.

1,413,405. Patented Apr. 18,; 1922.

- 2 SHLFTS-SHEET I.

1 r l I I l I l I I i H [3 AT QIZNBYS w. s. HEWE TT. REENFORCED CONCRETE PIPE.

APPLICATION FILED JUNEZI, 192!- 2 SHEETS-SHEET 2.

Hi6 ATi'ONEYS iToall who'm-it may concern. Y Be itknown that L'WILLIAM S. Hawn'r'r,

wherein the walls are by hydraulic or pneumatlc pressure. has

been customary in the present methods of I UNITE-l )?STAT-ES" PATENT- oFFicE.

witmm s; nnwn'rr, or unmmronis, umnasorgs .nnmmoncnnsconcnmn PIPE.-

Spec iflcation of Iietters Patent.

,, aten ted Apr. 18; 1922.

* Application filed Jui1e27, 1921. ."serial m 480,633. 1

a citizen of the United States, resident of Minneapolis, county of Hennepin, State of .Minnesota, have invented certain new and useful Improvements in Reenforced-Con- I crete Pipe, of which the following is a specification' My. invention relates to reenforced concrete pressure pipe or similar structures putuIider tension construction to embed the rods in the concrete in such a mannerthat the normal shrinkage ofthe concrete in setting causes compression in the rods and tension in the concrete when the pipe is empty. When the pipe is filled with water or other material under pressure, it tends to expand and further tension is put upon the concrete in I the efiiciency of .the pipe Walls, resulting in'cracks and leaks.

The size of the cracks depends, of course, upon the degree of expansion and outward pressure, but very. small cracks resulting from the separation of the particles of con;

.crete will-permit the escape of a liquid under pressure 'in the pipe and impair seriously t e pipe as a liquid holding or transportingmeans; On the other hand, it is well known that concrete in compression is practically water-tight.

-The object, therefore, of my invention is to provide areenforced concrete wall, no part of which shall be under tension even when subjected to hydraulic or pneumatic pressure.

A further object is to provide a reen-.

forced'concrete wall in which a considerable saving can be effected in the amount of concrete and steel required to obtain a watertight structure.

My invention consists generally in placing rods in the wall of a fluid pressure pi e under an initial tension equal approximate y to the working stress of the. pipe, thereby placing the inner portion of the wall encircled by the rod under compression and preventing the formation of cracks therein when it is subjected to outward pressure or tension.

Further the invention consists in various constructions and combinations, all as hereinafter described and particularly pointed out in the claims.

' In the accompanying part of thisspeclfication,

} Figure 1 is an elevationof a reenforcerl concrete 'pipe,'partially in section, to show the location of the reinforcing rods therein,

Figure 2 is a drawings formingof Figure 1',"

Figure 3 is a sectional view of a joint in the pre-molded reenforced concrete pipe,

Figure 4 is a sectional view" through the band of Figure '3.

In'the drawing, I have shown a conventional form :of. reenforced concrete water p1p'e embodying my invention. It will be understood, however, that I do not confine sectional view of the'device myself to this structure, as the invention is capable-of use wherever it is desired to In. the drawings, I have shown a reen forced concrete pipe for conveying water or other liquid under pressure. When this pipe is filled with liquid, the walls of the pipe will be subjected to high tensile stresses. ing such a plpe. is to place the reinforcing rods in the concrete whenthe pipe is moulded. -After these pipes are moulded the shrinkage ofthe concrete in setting causes compression inthe steel and tension "in the concrete. These stresses are a reversal of the desiredstresses as the pipe is designed to withstand pressure with the steel in tension. When water pressure is added the resultant forces cause an additional tension in concrete with the result that the concrete fails and expands until the entire pressure is resisted by the tension in the rods. The high tension in the concrete and rods under an initial tension so that the inner portion of the walls of the pipe are in compression and in doing this I may employ the following method.

The interior of the pipe lying within the rods as shown at A in Figures 2 and The usual method of construct-v prevent cracking of concrete under tension."

5, is first moulded and alldwed to partially set. This allows the shrinkage to take place turning turnbucklesfC until they are subjected to the desired initial stress, and this puts the concrete A within the rods in compression. The concrete D lying outside the rods B is then put in place. This coating may be placed by moulding it in forms, by plastering, or by the use of gunite. This outer coating of concrete protects the rods from corrosion, furnishes additional bearing for the rods and provides additional precaution against leakage.

This method of construction also permits a simple method in making joints in premoulded reenforced concrete pipe. Figure 3 shows a joint in premoulded pipe using my methods. E and F (Figure 3) are two pieces of pipe to be joined. A band is premoulded in sections H (Figures 2 and 4). These sections are then assembled around the pipe and adjustable rods J (Figure 3) are placed and. tightened up by the use of turnbuckles C with enough lnitial tension in said rods toequal or more than equal the pressure to which the pipe is to' be subjected. These rods are then buried in concrete placed by any convenient method, such as herein specified for covering the rods in the pipe. A-gasket K of lead, felt or other suitable material, may be inserted between :hetband and the pipe to insureperfect conac This method of construction will result in considerable economy. The old method of constructing reenforced concrete pressure pipe called for a low unit stress on steel to.

avoid high tension in concrete. My inventlon by avoiding shrinkage stresseswill permlt a large unit stress in steel resulting in material saving. Under the old method of construction'the concrete is always in tension. In my method of construction the concrete is in compression and never in tension. As thejallowable unit stress. of con.-

crete in compression is more than ten times the allowable un t stress of concrete in tension I make a material saving in concrete. It should .benotedj -that I make no claim for invention on the manner of tighteningthe rodswhether byturnbuckle, by nut and screw end or other method. My claim for invention lies in tightening the rods to a a known intensity giving a desired initial stress 1n the rods before such rods are buried in the concrete.

tension under an assumed-loadin and measured initial stress, and then placing additional concrete imbedding said rods in such I manner as' to furnish additional;

bearings for said rods;

"2. A method of reenforcingicircular. concrete structures subject to internal press ...1 v

which consists in placing around a hardened inner core of such structure, separate' circu- This enables the designer. to know that the concrete will not beriiln intensity of-the lnitia'l stress on t e rods may be accurately measured by knowing and power applied 1 lar iron or steel bands each with adjustable means, and adjusting each band to a known 7 I and measured initial stress of such intensity as to balance internal pressure and then placing additional concrete, imbedding said bands in such vmanner as to furnish addi x f tional bearings for said rods.

3. -A method of joining concrete pipe tions which consists ,in placing theends'of the sections in abutting relation, assembling around the joint a band provided Wlt tightening means then tightening theband' to a de ree equal or'more than equal to I outwar pressure to which the pipe will 'be subjected. a

4. A method of joining concreg-p'ip sec;

tions which consists in placing the ends of the sections in abutting relation, assembling; 3 around the joint a gasket and around the. gasket a 'band provided with means for..

tightening the Same, ntighaning bands to a degree equal or-more than equal. to the outward pressure -to which the plpe" will besubjected, I j j In witness whereof, I have hereunto. set my-hand this 22nd da of June, 1921.

WILL AM s. EwETr. 1 5 

